The present invention relates to an automated teller machine including a secure enclosure within which a plurality of teller machine utilities are disposed. Such utilities may comprise a currency dispenser and a depository for the deposit of currency, cheques or other financial instruments.
It is necessary for an automated teller machine to be secured against unauthorized access which could result in the fraudulent operation of the utilities which form part of the teller machine. Nevertheless it is necessary for the teller machine to be in data communication with a host data processor which provides control data to operate the teller machine. Such data communication takes place conventionally through an input port into the secure enclosure of the machine.
It is known to utilize a serial data bus for communication from a host processor to the utilities of the teller machine. The utilities are connected to the data bus in a serial "daisy chain" fashion so that the utilities are addressable through the serial bus linking the utilities. The communications with the individual utilities are encrypted in an attempt to combat the unauthorized interception of communications between the host processor and the teller machine and the communication of fraudulent messages over the serial link. Nevertheless, a breach in the security of the encryption codes will compromise the security of operation of the teller machine.
A need therefore exists to improve on the level of security beyond that provided by the use of encryption codes between a host processor and a teller machine.